I tried different crystal manufacturers, I tried a ceramic resonator and I applyed an external clock but the result is the same
I found a new information :
If I put a delay of 100ms between VddIO and Vdda_ADC, the DSC starts-up.
The VddIO has to apply after Vdda_ADC of the DSC.
Have you an explanation about that ?
Generally, you can use digital 3.3V(connected to VDDIO) to generate analog 3.3V(connected to VDDA) via a ferrite bead, while, you can connect a ferrite bead between VSS and VSSA.
I have checked the data sheet of MC56F8355, I have not seen the power-up sequence requirement for VDDIO and VDDA.
It appears that the crystal works unreliably, pls refer to the configuration I copied from Data sheet:
From software, you have to set the OCCS_OSCTL[COHL]=1.
Pls add two caps on the EXTAL/XTAL pins and have a try. If you still have question, pls change another 8MHz crystal from different manufacturer.
Hope it can help you